I wanted to drag all the .jpg files onto the image processing application.
The problem is that the files are located in a lot of subdirectories.
Actually, the real problem is the Mac Finder, which blows bits.
One of these days, I'm going to write a Finder that behaves like the Windows XP File Explorer.
In the meantime, I get to use some Bash and command line fu to get the job done.
$ cd /directory-to-place-all-links
$ find /root-image-directory . -name '*.jpg' -type f -exec ln -s {} . \;
Now, I can drag all the files (links) to the image processing application window.